CN115753854A

CN115753854A - Method for preparing titanium alloy EBSD sample by additive manufacturing through chemical polishing

Info

Publication number: CN115753854A
Application number: CN202211459485.1A
Authority: CN
Inventors: 王震; 徐嘉朦; 徐刚; 伊启中
Original assignee: Fujian University of Technology
Current assignee: Fujian University of Technology
Priority date: 2022-11-17
Filing date: 2022-11-17
Publication date: 2023-03-07

Abstract

The invention discloses a method for preparing an additive manufactured titanium alloy EBSD sample by chemical polishing, which comprises the following steps: grinding the titanium alloy test surface by using abrasive paper until no obvious scratch is formed, then dipping a chemical polishing agent in absorbent cotton to wipe the test surface of the titanium alloy test sample, cleaning the test surface, drying the test surface by blowing the test surface, repeating the steps until the test surface is flat and bright, and observing no scratch under a microscope to obtain an EBSD sample; wherein the chemical polishing agent is a chemical polishing solution A consisting of hydrofluoric acid, nitric acid and lactic acid, or a chemical polishing solution B consisting of hydrofluoric acid, nitric acid, lactic acid and glycerol. The chemical polishing method disclosed by the invention is simple and efficient to operate, has a high EBSD (electron back scattering diffraction) resolution ratio when being used for additive manufacturing of the titanium alloy, particularly has a better corrosion inhibition effect on an acid solution because a proper amount of glycerol is added into the chemical polishing solution B, solves the problems of over-quick corrosion and uneven corrosion of the titanium alloy during additive manufacturing, and ensures that the surface of a sample is smooth.

Description

Method for preparing titanium alloy EBSD sample by additive manufacturing through chemical polishing

Technical Field

The invention relates to the field of metal material processing, in particular to a method for preparing an additive manufacturing titanium alloy EBSD sample by chemical polishing.

Background

The microstructure of the titanium alloy mainly consists of alpha + beta phase, and has good mechanical property, corrosion resistance and biocompatibility, so that the titanium alloy is widely applied to the fields of aerospace and biomedicine. In the forming process of the additive manufacturing titanium alloy, the additive manufacturing titanium alloy is influenced by factors such as cooling rate, thermal stress and the like, and cracks and delamination phenomena may occur during solidification, so that the service performance of the additive manufacturing titanium alloy is seriously influenced. Therefore, it becomes important to explore the microstructure and stress distribution of the titanium alloy for additive manufacturing to solve the above problems. The Electron Back Scattering Diffraction (EBSD) technology is an advanced technology in the field of material analysis, combines the microstructure with the crystallography analysis, can not only carry out the microstructure analysis, but also carry out the analysis of orientation, strain and the like, provides theoretical support for improving the performance of the additive manufacturing titanium alloy, and has important application value.

The EBSD technique requires high requirements for the test sample, not only requiring the test sample surface to have high flatness, but also requiring no residual stress. The conventional method for preparing the titanium alloy EBSD sample comprises vibration polishing, ion polishing, electrolytic polishing and the like. The EBSD sample preparation is carried out by adopting the vibration polishing machine, strict requirements are imposed on the size of a sample, and the vibration amplitude and the load of the polishing machine have great influence on the quality of the EBSD sample and need to be explored for a long time. And the ion polishing is adopted, so that the equipment is expensive, the processing period is long, and the sample preparation cost is high. Electrolytic polishing is a common method for preparing titanium alloy EBSD samples, but the method has high experimental requirements and low success rate. Through the search of patent documents, the Chinese patent application with the application number of 201810601742.8 discloses an electrolytic polishing method for preparing pure titanium and titanium alloy EBSD samples. Chinese patent with application number CN201910921930.3 discloses a preparation method of an EBSD sample of a titanium alloy fracture section. The temperature of the electrolytes of the above two patent applications must reach-30 deg.C to-10 deg.C, and the electrolytic polishing is very sensitive to polishing voltage, current, time and temperature. Compared with the various polishing methods, the chemical polishing method has the advantages of simple operation, high efficiency, low cost and low requirements on experimental conditions, and is an ideal preparation method for additive manufacturing of titanium alloy EBSD samples.

Disclosure of Invention

The invention aims to provide a method for preparing an additive manufacturing titanium alloy EBSD sample by chemical polishing, which is simple to operate, low in cost and high in efficiency.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for preparing an additive manufacturing titanium alloy EBSD sample by chemical polishing comprises the following steps:

(1) Cutting a titanium alloy sheet, and sequentially using 200#,800#,1200#,2000#,3000# and 5000# sandpaper to grind a titanium alloy test surface to obtain a pretreated titanium alloy sample;

(2) Dipping a chemical polishing agent in absorbent cotton to wipe the test surface of the pretreated titanium alloy sample in a rapid reciprocating manner for 4 to 6 seconds, then cleaning the test surface by using deionized water and an ethanol solution, and then drying the test surface by blowing;

(3) And (3) repeating the step (2) until the test surface is flat and bright, and no scratch is observed under a 500X microscope, so as to obtain the EBSD sample.

The chemical polishing agent is a chemical polishing solution A consisting of hydrofluoric acid solution, nitric acid solution and lactic acid solution, wherein the volume percentages of the hydrofluoric acid solution, the nitric acid solution and the lactic acid solution are respectively 6% -8%, 40% -60% and 32% -54%, and the sum of the volume percentages of the three solutions is 100%.

Preferably, the volume percentages of the hydrofluoric acid solution, the nitric acid solution and the lactic acid solution in the chemical polishing solution A are 8%, 55% and 37%, respectively.

Further, the chemical polishing agent is a chemical polishing solution B composed of a hydrofluoric acid solution, a nitric acid solution, a lactic acid solution and glycerol, wherein the hydrofluoric acid solution, the nitric acid solution, the lactic acid solution and the glycerol are respectively 6% -8%, 50% -70%, 12% -39% and 5% -10% in volume percentage, and the sum of the volume percentages of the four solutions is 100%. And a proper amount of glycerol is added into the chemical polishing solution B, so that a better corrosion inhibition effect is achieved on an acid solution, the problems of over-fast corrosion and uneven corrosion of the titanium alloy manufactured by the additive are solved, and the surface of a test sample is ensured to be flat.

Preferably, the volume percentages of the hydrofluoric acid solution, the nitric acid solution, the lactic acid solution and the glycerol in the chemical polishing solution B are respectively 8%, 60%, 27% and 5%.

The mass concentration of the hydrofluoric acid solution is 40% -50%, the mass concentration of the nitric acid solution is 65% -68%, the mass concentration of the lactic acid solution is 85.5% -90%, and the mass concentration of the glycerol is 90% -98%.

In the step (1), when 2000#,3000# and 5000# sandpaper is adopted for grinding, grinding with water is carried out.

In the step (1), when sand papers of different models are changed, the titanium alloy is rotated by 90 degrees along the same direction and then ground until no obvious scratch is formed on the test surface after the No. 5000 sand paper is ground.

In the step (2), the chemical polishing agent is washed by using deionized water and absolute ethyl alcohol alternately until no residue exists on the surface of the sample. And cleaning with deionized water for 5 to 10s, then washing the chemical polishing agent on the surface of the sample with absolute ethyl alcohol, after the chemical polishing agent is treated for the last time, cleaning with water for 5 to 10s, and then ultrasonically cleaning with absolute ethyl alcohol for 5 to 10min.

Furthermore, the number of times of the chemical polishing agent treatment is 5 to 10.

By adopting the technical scheme, the surface of the titanium alloy is ground by sand paper until no obvious scratch exists, the pretreatment is completed, and then the corrosion treatment is carried out by using a chemical polishing agent, so that the titanium alloy surface polishing agent has the beneficial effects that:

1. grinding the titanium alloy sheet by 200#,800#,1200# dry abrasive paper, wetting and grinding by water sequentially by 2000#,3000# and 5000# abrasive paper to obtain a preliminarily pretreated titanium alloy sample, and grinding by water by adopting high-number abrasive paper, so that obvious scratches on the surface of the titanium alloy can be effectively removed, and the influence of subsequent scratches on the preparation of the titanium alloy EBSD sample is reduced.

2. And (3) dipping chemical polishing agent in absorbent cotton, quickly wiping the surface of the sample, removing corrosion products on the surface, and realizing smooth and bright surface and stress-free layer.

3. The polishing solution is mainly hydrofluoric acid, nitric acid and lactic acid solution, and glycerin is used as a corrosion inhibitor of acid to adjust the sensitivity of the strong acid solution to the corrosivity of the microstructure of the titanium alloy manufactured by additive manufacturing, so that the problem of insufficient EBSD calibration rate of the conventional chemical polishing method for the titanium alloy manufactured by additive manufacturing is solved.

4. The chemical polishing agent comprises hydrofluoric acid, nitric acid, lactic acid and glycerol, is low in price, is a common solvent in a laboratory, and is easy to obtain.

5. Compared with the methods of electrolytic polishing, ion polishing and the like, the method for preparing the titanium alloy EBSD sample by adopting chemical polishing has the advantages of simple and convenient operation, low cost, higher preparation success rate and efficiency and smaller danger.

6. The chemical polishing method is simple and efficient to operate, is used for additive manufacturing of the titanium alloy EBSD, and is high in resolution.

Drawings

FIG. 1 is an EBSD map of additive manufactured Ti-6Al-4V samples prepared from example 1 by treatment with chemical polishing solution A.

FIG. 2 is an EBSD map of additive manufactured Ti-6Al-4V samples prepared from example 2 by treatment with chemical polishing solution B.

FIG. 3 is a plot of the distribution of the large and small angle grain boundaries of the additive manufactured Ti-6Al-4V samples prepared from example 2 by treatment with chemical polishing solution B.

Detailed Description

The invention is further described in detail below with reference to the drawings and the detailed description.

Example 1

1) Cutting a slice from a Ti-6Al-4V sample to be tested which needs to be observed in additive manufacturing by utilizing a linear cutting technology, grinding the slice by sequentially using 200#,800#,1200# dry abrasive paper, wet grinding the slice by using 2000#,3000# and 5000# abrasive paper, grinding the Ti-6Al-4V sample to be tested after rotating the sample for 90 degrees along the same direction when different types of abrasive paper are changed, until no obvious scratch exists on a test surface after the 5000# abrasive paper is ground, then ultrasonically cleaning the sample for 10min, and drying.

2) Hydrofluoric acid with the mass concentration of 45%, nitric acid with the mass concentration of 66.5% and lactic acid with the mass concentration of 88% are mixed to form chemical polishing solution A, and the three solutions respectively account for 8%, 55% and 37% of the chemical polishing solution A in volume percentage.

3) Dipping absorbent cotton into the chemical polishing solution A, quickly wiping the additive manufacturing Ti-6Al-4V test surface for 4-6 s, alternately cleaning the test surface by using deionized water and absolute ethanol solution, then drying the test surface by blowing, repeatedly wiping the test surface for 8 times according to the corrosion effect until no scratch is observed on the test surface under a 500X microscope to obtain an EBSD sample, and carrying out a back scattering electron diffraction test on the obtained additive manufacturing titanium alloy EBSD sample, wherein the calibration rate is 91%, and the experimental result is shown in figure 1.

Example 2

2) Hydrofluoric acid with the mass concentration of 45%, nitric acid with the mass concentration of 66.5%, lactic acid with the mass concentration of 88% and glycerol with the mass concentration of 95% are mixed to form chemical polishing solution B, and the four solutions respectively account for 8%, 60%, 27% and 5% of the chemical polishing solution B in volume percentage.

3) Dipping absorbent cotton into the chemical polishing solution B, quickly wiping the additive manufacturing Ti-6Al-4V test surface for 4-6 s, alternately cleaning the test surface by using deionized water and absolute ethyl alcohol solution, drying the test surface by blowing, repeatedly wiping the test surface for 8 times according to the corrosion effect until no scratch is observed on the test surface under a 500X microscope until no scratch is observed on the test surface under the 500X microscope, obtaining an additive manufacturing titanium alloy EBSD sample, and performing a back scattering electron diffraction test on the obtained additive manufacturing EBSD sample, wherein the standard rate is 93%, and the experimental result is shown in figure 2.

The titanium alloy EBSD samples obtained in the embodiment 1 and the embodiment 2 are respectively shown in figures 1 and 2 after calibration, the calibration rates are 91% and 93%, and the comparison shows that the figure 2 has a clearer texture map, and the figure 1 has poorer quality.

Therefore, the high-standard EBSD can be efficiently prepared by using the chemical polishing agent A or the chemical polishing agent B, and meanwhile, the calibration rate of the chemical polishing agent B is obviously improved, so that more accurate data can be obtained.

Claims

1. A method for preparing an additive manufacturing titanium alloy EBSD sample by chemical polishing is characterized by comprising the following steps:

(1) Grinding the titanium alloy test surface by using abrasive paper until no obvious scratch exists, and finishing pretreatment to obtain a titanium alloy test sample;

(2) Wiping the test surface of the titanium alloy sample by using absorbent cotton dipped with a chemical polishing agent for 4 to 6 seconds, then cleaning the test surface by using water and an ethanol solution, and then drying the test surface by blowing;

the chemical polishing agent is a chemical polishing solution A consisting of hydrofluoric acid solution, nitric acid solution and lactic acid solution according to volume percentages of 6-8%, 40-60% and 32-54%, and the sum of the volume percentages of the three solutions is 100%;

(3) And (3) repeating the step (2) until the test surface is flat and bright, and no scratch is observed under a 500X microscope to obtain an EBSD sample.

2. The method for preparing the additive manufactured titanium alloy EBSD sample by chemical polishing as claimed in claim 1, wherein the volume percentages of the hydrofluoric acid solution, the nitric acid solution and the lactic acid solution in the chemical polishing solution A are respectively 8%, 55% and 37%.

3. The method for preparing the additive manufacturing titanium alloy EBSD sample through chemical polishing according to claim 1, wherein the chemical polishing agent further comprises glycerol, and the glycerol is a chemical polishing solution B composed of 6-8% by volume, 50-70% by volume, 12-39% by volume and 5-10% by volume of hydrofluoric acid solution, nitric acid solution, lactic acid solution and glycerol, and the sum of the volume percentages of the four solutions is 100%.

4. The method for preparing the additive manufactured titanium alloy EBSD sample by chemical polishing as claimed in claim 3, wherein the volume percentages of the hydrofluoric acid solution, the nitric acid solution, the lactic acid solution and the glycerol in the chemical polishing solution B are respectively 8%, 60%, 27% and 5%.

5. The method for preparing the additive manufacturing titanium alloy EBSD sample through chemical polishing according to claim 3, wherein the mass concentration of the hydrofluoric acid solution is 40% -50%, the mass concentration of the nitric acid solution is 65% -68%, the mass concentration of the lactic acid solution is 85.5% -90%, and the mass concentration of the glycerol is 90% -98%.

6. The method for preparing the titanium alloy EBSD sample by the chemical polishing according to claim 1, wherein the step (1) is as follows: cutting a titanium alloy sheet, and sequentially using 200#,800#,1200#,2000#,3000# and 5000# sandpaper to grind the titanium alloy test surface to obtain a pretreated titanium alloy sample.

7. The method for preparing the additive manufactured titanium alloy EBSD sample by chemical polishing as claimed in claim 6, wherein the abrasive is carried out with water when 2000#,3000# and 5000# sandpaper is adopted.

8. The method for preparing the titanium alloy EBSD sample by chemical polishing as claimed in claim 6, wherein when different types of sand paper are used, the titanium alloy is rotated by 90 degrees along the same direction and then ground until no obvious scratch is formed on the test surface after 5000# sand paper grinding.

9. The method for preparing the additive-manufactured titanium alloy EBSD sample by chemical polishing as claimed in claim 1, wherein in step (2), the chemical polishing agent is washed by water and absolute ethyl alcohol alternately until no residue is left on the surface of the sample, and after the last chemical polishing agent treatment, the sample is washed by water for 5 to 10s and then is washed by absolute ethyl alcohol for 5 to 10min in an ultrasonic mode.

10. The method for preparing the titanium alloy EBSD sample by chemical polishing as claimed in claim 1, wherein the number of the repeated chemical polishing agent treatments is 5-10.